U.S. patent application number 12/019587 was filed with the patent office on 2008-07-31 for motorcycle.
This patent application is currently assigned to YAMAHA HATSUDOKI KABUSHIKI KAISHA. Invention is credited to Yousuke ISHIDA, Akifumi OISHI.
Application Number | 20080179127 12/019587 |
Document ID | / |
Family ID | 39304856 |
Filed Date | 2008-07-31 |
United States Patent
Application |
20080179127 |
Kind Code |
A1 |
OISHI; Akifumi ; et
al. |
July 31, 2008 |
Motorcycle
Abstract
A motorcycle including a belt type continuously variable
transmission (CVT) and having a reduced width. An engine unit
includes an engine having a crank shaft, the belt type CVT, a
clutch, an output shaft and a generator. The CVT has a primary
sheave, a secondary sheave shaft and a secondary sheave. The
primary sheave is on one side of the crank shaft and the clutch is
on another side with respect to the secondary sheave on the
secondary sheave shaft. The output shaft is on a side opposite to
the clutch on the secondary sheave shaft. The generator is on the
other side of the crank shaft. A center axis of rotation of the
secondary sheave shaft is higher than a center axis of rotation of
the crank shaft. Right and left footsteps are located behind a rear
end of the rotation motor and under a lower end of the secondary
sheave.
Inventors: |
OISHI; Akifumi; (Shizuoka,
JP) ; ISHIDA; Yousuke; (Shizuoka, JP) |
Correspondence
Address: |
HOGAN & HARTSON L.L.P.
1999 AVENUE OF THE STARS, SUITE 1400
LOS ANGELES
CA
90067
US
|
Assignee: |
YAMAHA HATSUDOKI KABUSHIKI
KAISHA
Iwata-shi
JP
|
Family ID: |
39304856 |
Appl. No.: |
12/019587 |
Filed: |
January 24, 2008 |
Current U.S.
Class: |
180/230 ;
180/219 |
Current CPC
Class: |
B62J 25/00 20130101 |
Class at
Publication: |
180/230 ;
180/219 |
International
Class: |
B62K 11/00 20060101
B62K011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 26, 2007 |
JP |
2007-016493 |
Claims
1. A motorcycle comprising: an engine unit; and right and left
footsteps, wherein the engine unit comprises: a crank shaft; a belt
type continuously variable transmission including a primary sheave
provided on one side of the crank shaft in a vehicle width
direction, a secondary sheave shaft provided behind the crank shaft
and a secondary sheave provided on the secondary sheave shaft; a
clutch provided on another side in the vehicle width direction with
respect to the secondary sheave on the secondary sheave shaft; and
a rotation motor provided on the other side of the crank shaft in
the vehicle width direction, and a center axis of rotation of the
secondary sheave shaft is provided at a position higher than a
center axis of rotation of the crank shaft while at least a part of
the right and left footsteps is located behind a rear end of the
rotation motor and under a lower end of the secondary sheave.
2. The motorcycle according to claim 1, wherein at least a part of
the right and left footsteps is located in front of a rear end of
the secondary sheave.
3. The motorcycle according to claim 1, wherein at least a part of
the right and left footsteps is located behind a front end of the
secondary sheave.
4. The motorcycle according to claim 1, further comprising: a body
frame provided with the engine unit; a pivot shaft mounted to the
body frame; a rear arm swingably mounted to the pivot shaft; and a
rear wheel rotatably mounted to the rear arm, wherein the pivot
shaft is provided above at least a part of right and left footsteps
and under the center axis of rotation of the secondary sheave
shaft.
5. The motorcycle according to claim 4, wherein the pivot shaft is
provided at a height substantially equal to that of the center axis
of rotation of the crank shaft.
6. The motorcycle according to claim 1, wherein an upper end of the
right and left footsteps is located above a lower end of the engine
unit.
7. The motorcycle according to claim 1, further comprising: a body
frame provided with the engine unit and including a steering head
pipe, wherein the engine unit further includes a piston between the
primary sheave and the rotation motor, the piston connected to the
crank shaft and extending in a back-and-forth direction in flat
view, and a center line of the piston extending in the
back-and-forth direction is located on one side of a center line of
the steering head pipe, in flat view.
8. The motorcycle according to claim 7, further comprising: a cam
chain wound around a part located on one side of a part of the
crank shaft connected to the piston, in the vehicle width
direction.
9. The motorcycle according to claim 1, wherein at least a part of
the right and left footsteps is located in a concave part behind
the rotation motor.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of priority under 35 USC
119 of Japanese patent application no. 2007-016493, filed on Jan.
26, 2007, which application is hereby incorporated by reference in
its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to a motorcycle having a belt type
continuously variable transmission.
[0004] 2. Description of Related Art
[0005] An engine unit including an engine and a belt type
continuously variable transmission (CVT) is disclosed, for example,
in JP-A-2006-168468.
[0006] The engine unit of JP-A-2006-168468 is wide since the belt
type CVT is located on an outer side of a piston of the engine in a
vehicle width direction. Thus, a footstep of the motorcycle to
which the engine unit is mounted projects greatly in the vehicle
width direction. Accordingly, there is a problem in that it is
difficult to downsize the vehicle body in width.
SUMMARY OF THE INVENTION
[0007] In view of the above, the invention downsizes in width a
vehicle body of a motorcycle to which an engine unit including a
belt type CVT is mounted.
[0008] A motorcycle in accordance with the invention comprises an
engine unit and right and left footsteps. The engine unit comprises
an engine; a belt type CVT; a clutch; and a rotation motor. The
engine includes a crank shaft. The belt type CVT includes a primary
sheave, a secondary sheave shaft and a secondary sheave. The
primary sheave is provided on one side of the crank shaft in a
vehicle width direction. The secondary sheave shaft is provided
behind the crank shaft. The secondary sheave is provided on the
secondary sheave shaft. The clutch is provided on another side in
the vehicle width direction with respect to the secondary sheave on
the secondary sheave shaft. The rotation motor is provided on the
other side of the crank shaft in the vehicle width direction.
[0009] In the motorcycle in accordance with the invention, a center
axis of rotation of the secondary sheave shaft is provided at a
position higher than a center axis of rotation of the crank shaft.
At least a part of the right and left footsteps is located behind a
rear end of the rotation motor and under a lower end of the
secondary sheave.
[0010] In accordance with the invention, the width of the
motorcycle is reduced.
[0011] Other features and advantages of the invention will be
apparent from the following detailed description, taken in
conjunction with the accompanying drawings which illustrate, by way
of example, various features of embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a right side view of a motorcycle according to an
embodiment of the invention.
[0013] FIG. 2 is a right side view of a center portion of the
motorcycle.
[0014] FIG. 3 is a sectional view of an engine unit of the
motorcycle.
[0015] FIG. 4 is a right side view of a part of the engine
unit.
[0016] FIG. 5 is a sectional, plan view of a part of the
motorcycle.
DETAILED DESCRIPTION OF THE INVENTION
[0017] <<Outline of Embodiment>>
[0018] An embodiment of the invention relates to an off-road type
motorcycle 1 in which at least a part of a pair of right and left
footsteps 30 is located behind a rear end of a generator 29 and in
which an engine unit 12 including a belt type CVT 14 is mounted, as
shown in FIGS. 1 and 3. A center axis of rotation A1 of a secondary
sheave shaft 38 is higher than a center axis of rotation A2 of a
crank shaft 20, and at least a part of footsteps 30 is located
under secondary sheave 37, as shown in FIG. 4. This allows
footsteps 30 to be provided further inward in the vehicle width
direction and reduces vehicle width.
[0019] While motorcycle 1 is described as an off-road type, the
invention is not so limited. In the invention, a motorcycle means a
motorcycle in the broad sense and includes a motor scooter and a
moped, for example.
[0020] <<Structure of Motorcycle 1>>
[0021] FIG. 1 is a side view of a motorcycle 1. FIG. 2 is a right
side view of a center portion of motorcycle 1. In the following
description, the back-and-forth and lateral directions are from the
perspective of a driver sitting on a seat 11.
[0022] Motorcycle 1 has a body frame 2. Body frame 2 comprises a
steering head pipe 3, down tube 4 and a seat pillar 5. Down tube 4
extends downward from steering head pipe 3. Seat pillar 5 extends
rearward from steering head pipe 3 above down tube 4. A supporting
member 31 is mounted to and extends forward from a lower end of
seat pillar 5. Right and left footsteps 30, on which feet 60 of a
driver are put, are mounted to a top end of supporting member 31
(refer to FIG. 5). A kick shaft 70 is provided above footstep 30,
as shown in FIG. 2.
[0023] A lower end of steering head pipe 3 is connected to a front
wheel 7 through a front fork 6 or the like. A rear arm 8 is
pivotably supported in the vicinity of a lower end of seat pillar 5
and extends rearward. In detail, a base end of rear arm 8 is
pivotably supported on a pivot shaft 5a connected to seat pillar 5.
A top (rear) end of rear ram 8 is connected to a rear wheel 9. A
cover 10 covers body frame 2. A seat 11 is fitted on a somewhat
rear side of the center of cover 10.
[0024] Engine unit 12 is provided between and mounted to (suspended
on) down tube 4 and seat pillar 5. Engine unit 12 comprises an
engine 13, CVT 14, a centrifugal clutch 15, a generator 29 and a
reduction mechanism 16, which are integrated into one body. Driving
force generated in engine unit 12 is transmitted to rear wheel 9
through a power transmitting means such as a chain belt.
[0025] --Structure of Engine Unit 12--
[0026] Engine unit 12 is described primarily with reference to FIG.
3. As noted above, engine unit 12 comprises engine 13, belt type
CVT 14, centrifugal clutch 15, reduction mechanism 16 and generator
29. For sake of convenience, reduction mechanism 16 is partially
omitted from FIG. 3.
[0027] (Unit Case 50)
[0028] Engine unit 12 is housed in a unit case 50. Unit case 50
comprises a crank case 51, a generator case 54 and a transmission
case 55. A crank shaft 20 is housed in crank case 51. Crank case 51
is formed from a first case block 52 and a second case block 53,
which face each other in the vehicle width direction. First case
block 52 is located on the left side of piston 23. Second case
block 53 is located on the right side of piston 23.
[0029] Transmission case 55 is mounted on the right side of crank
case 51 (concretely, second case block 53). Transmission case 55 is
formed from an inner case 56 and an outer case 57. Inner case 56 is
mounted on the right side of crank case 51 (concretely, second case
block 53). Outer case 57 is mounted on the right side of inner case
56. A belt chamber 34 is formed by outer case 57 and inner case
56.
[0030] Generator case 54 is detachably mounted on the left side of
a front half part of first case block 52. Generator case 54 divides
a space to form a generator chamber for housing generator 29
together with first case block 52. Generator case 54 is provided at
a position opposite to primary sheave 36 in the vehicle width
direction to form an expanded part of unit case 50.
[0031] A length L1 in the vehicle width direction from a center
line C2 of engine 13 extending in the back-and-forth direction to
an outer end 54a of generator case 54 is longer than a length L2
from center line C2 of engine 13 to an outer end 55a of a part of
transmission case 55 that houses primary sheave 36. That is,
generator case 54, which forms the expanded part, expands in the
vehicle width direction more than the part of transmission case 55
for housing primary sheave 36.
[0032] (Engine 13)
[0033] Engine 13 comprises crank shaft 20 extending horizontally in
the vehicle width direction, a cylinder 18 and a cylinder head 19.
Crank shaft 20 is housed in crank case 51 and is supported on first
and second case blocks 52 and 53 through bearings 21 and 22.
[0034] Cylinder 18 is connected obliquely upward in front of crank
case 51 (see also FIG. 1). Cylinder head 19 is connected to a top
end of cylinder 18. Piston 23 is slidably inserted into cylinder
18. Piston 23 is connected on a crank shaft 20 side thereof to one
end of a connection rod 24. The other end of connection rod 24 is
connected to a crank pin 17 provided between a left crank arm 20a
and a right crank arm 20b of crank shaft 20. Accordingly, piston 23
reciprocates in cylinder 18 in accordance with rotation of crank
shaft 20.
[0035] A concave part 19a connected to an inner space of cylinder
18, and intake and exhaust ports that communicate to concave part
19a, are formed in cylinder head 19 An ignition plug 25 is fixedly
inserted in cylinder head 19 so that an ignition part at a top end
of ignition plug 25 is exposed in concave part 19a.
[0036] A cam chain chamber 26 for connecting inner parts of crank
case 51 and cylinder head 19 is formed on a left side of cylinder
18. A cam chain 27 inside cam chain chamber 26 is wound around
crank shaft 20 and cam shaft 28. This allows cam shaft 28 to rotate
in accordance with rotation of crank shaft 20, so that an intake
valve and an exhaust valve are opened and closed.
[0037] An opening formed on the right side of a rear half part of
second case block 53 is closed by a clutch cover 32. Clutch cover
32 is detachably fixed to second case block 53 by a bolt 33.
[0038] (Generator 29)
[0039] A left end of crank shaft 20 passes through first case block
52 to reach the inside of generator case 54. Generator 29 is
mounted to the left end of crank shaft 20 and comprises a rotor 29a
and a stator 29b. Rotor 29a is formed into the shape of a cylinder.
Stator 29b is provided in rotor 29a.
[0040] Stator 29b is fixed to generator case 54 so as not to rotate
and not to be displaced. On the other hand, rotor 29a is fixed to a
sleeve 35 rotating together with crank shaft 20. Rotor 29a thereby
rotates relative to stator 29b in accordance with rotation of crank
shaft 20, so that generation of electricity is carried out.
[0041] Belt type CVT 14 housed in belt chamber 34 comprises primary
sheave 36 and secondary sheave 37. Secondary sheave 37 is provided
behind primary sheave 36.
[0042] (Belt Type CVT 14)
[0043] Crank shaft 20 passes through second case block 53 and inner
case 56 to extend to belt chamber 34. A right side part of crank
shaft 20 having reached belt chamber 34 (strictly, a part on the
right side of bearing 22) forms a primary sheave shaft 20c. Primary
sheave 36 is mounted to primary sheave shaft 20c. Accordingly,
primary sheave 36 rotates together with crank shaft 20.
[0044] Primary sheave 36 comprises a primary fixing sheave body
36a, a primary movable sheave body 36b, a roller weight 44 and a
cam plate 43. Primary fixing sheave body 36a is fixed to a right
top end of primary sheave shaft 20c. Primary movable sheave body
36b is mounted to primary sheave shaft 20c on the left side of
primary fixing sheave body 36a. Primary movable sheave body 36b is
movable in an axial direction with respect to primary sheave shaft
20c. Primary fixing sheave body 36a and primary movable sheave body
36b form a belt groove 36c with a variable width.
[0045] Cam plate 43 provided on the further left side of primary
movable sheave body 36 is fixed to primary sheave shaft 20c. A
space between primary movable sheave body 36b and cam plate 43
narrows toward the outer side in the diameter direction. Roller
weight 44 is provided between primary movable sheave body 36b and
cam plate 43. Roller weight 44 can be displaced inward or outward
in the diameter direction.
[0046] A rear half of transmission case 55 is provided with a
secondary sheave shaft 38 substantially parallel to primary sheave
shaft 20c. Secondary sheave shaft 38 passes through inner case 56
and clutch cover 32 to extend to the inside of crank case 51.
Secondary sheave shaft 38 is mounted to clutch cover 32 through a
bearing 39. Secondary sheave 37 is mounted to secondary sheave
shaft 38 in belt chamber 34.
[0047] Secondary sheave 37 comprises a secondary fixing sheave body
37a and a secondary movable sheave body 37b. Secondary fixing
sheave body 37a is fixed to secondary sheave shaft 38 in belt
chamber 34. Secondary movable sheave body 37b is mounted to
secondary sheave shaft 38 on the right side of secondary fixing
sheave body 37a and is movable in an axial direction with respect
to secondary sheave shaft 38. Secondary fixing sheave body 37a and
secondary movable sheave body 37b form a belt groove 37c with a
variable width.
[0048] A spring stopper 47 is fixed to a right top end of secondary
sheave shaft 38. Urging force of a compression coil spring 45
provided between spring stopper 47 and secondary movable sheave
body 37b urges secondary movable sheave body 37b leftward, that is,
toward secondary fixing sheave body 37a.
[0049] A V belt (a resin block V belt, for example) 41 is wound
around belt groove 37c of secondary sheave 37 and belt groove 36c
of primary sheave 36. Accordingly, when primary sheave 36 rotates
together with crank shaft 20, torque thereof is transmitted to
secondary sheave 37 through V belt 41. This results in rotation of
secondary sheave shaft 38 together with secondary sheave 37.
[0050] A centrifugal clutch 15 is mounted to a part of secondary
sheave shaft 38 on the left side of clutch cover 32. Centrifugal
clutch 15 is connected to reduction mechanism 16 and connects and
disconnects secondary sheave shaft 38 and reduction mechanism 16 in
accordance with the rotation speed of secondary sheave shaft
38.
[0051] (Centrifugal Clutch 15)
[0052] Centrifugal clutch 15 comprises a clutch boss 15a connected
to reduction mechanism 16, a substantially cylindrical clutch
housing 15b and a roller weight 15c. Roller weight 15c is displaced
inward and outward in the diameter direction. Clutch housing 15b is
fixed to and rotates together with secondary sheave shaft 38.
Clutch housing 15b comprises plural clutch plates 15d provided at
substantially even intervals therebetween. The interval between
adjacent clutch plates 15d is variable.
[0053] Clutch boss 15a is provided in clutch housing 15b and is
rotatable with respect to secondary sheave shaft 38. Clutch boss
15a comprises plural friction plates 15e provided at substantially
even intervals therebetween. The interval between adjacent friction
plates 15e is variable.
[0054] Clutch plate 15d and friction plate 15e are separated from
each other, and clutch housing 15b is thus not connected to clutch
boss 15a, when secondary sheave shaft 38 is slow in rotational
speed. Accordingly, torque of secondary sheave shaft 38 is not
transmitted to reduction mechanism 16.
[0055] On the other hand, when the rotational speed of secondary
sheave shaft 38 is fast, roller weight 15c is displaced outward in
the diameter direction. This narrows a distance between adjacent
friction plates 15e such that clutch plates 15d and friction plates
15e are contacted by pressure. As a result, clutch housing 15b is
connected to clutch boss 15a, so that the torque of secondary
sheave shaft 38 is transmitted to reduction mechanism 16.
[0056] Torque transmitted to reduction mechanism 16 is output from
an output shaft 16a (FIG. 5) of reduction mechanism 16 to be
transmitted to rear wheel 9. Output shaft 16a is behind expanded
generator case 54, as shown in FIG. 5. Output shaft 16a is provided
in crank case 51. A left part of output shaft 16a passes through
crank case 51 to extend outside of crank case 51. A power
transmission means such as a chain is wound around the left side
part of output shaft 16a.
[0057] --Arrangement of Respective Structural Members of Motorcycle
1--
[0058] The arrangement of respective structural members of
motorcycle 1 is now described with reference to FIGS. 1-5.
[0059] (Arrangement of Engine Unit)
[0060] Engine unit 12 is provided so that center line C2 of piston
23 extending in the back-and-forth direction is located on the left
side of a center line C1 of steering head pipe 3 in flat view, as
shown in FIG. 5. In other words, center line C2 of engine 13 is
located on the left side of center line C1 of body frame 2. That
is, engine unit 12 is offset to the left side opposite to a side on
which belt type CVT 14 is provided.
[0061] (Arrangement of Primary Sheave 36 and Secondary Sheave
37)
[0062] On the other hand, in flat view, belt type CVT 14 extends
upward to the rear side, as shown in FIG. 4. The center axis of
rotation A1 of secondary sheave shaft 38 is located at a position
higher than the center axis of rotation A2 of crank shaft 20.
[0063] (Arrangement of Footstep 30)
[0064] As shown in FIG. 5, at least a part of footstep 30 is behind
a rear end 29c of generator 29. Further, at least a part of
footstep 30 is located in front of the rear end 37e of secondary
sheave 37 and behind front end 37f of the same. In addition, at
least a part of footstep 30 is located in a part where a left side
behind generator case 54 is concave. Output shaft 16a is similarly
provided in the part where a left side behind generator case 54 is
concave.
[0065] As shown in FIG. 4, at least a part of footstep 30 is
located under a lower end 37d of secondary sheave 37 in a
perpendicular direction. An upper end 30a of footstep 30 is located
above a lower end 12a of engine unit 12.
[0066] (Arrangement of Pivot Shaft 5a)
[0067] Pivot shaft 5a is provided above at least a part of footstep
30 and under the center axis of rotation A1 of secondary sheave
shaft 38. Concretely, pivot shaft 5a is provided at a height
substantially equal to that of the center axis of rotation A2 of
crank shaft 20.
[0068] <<Operation and Effect>>
[0069] Since engine unit 12 vibrates in running of motorcycle 1, a
comparatively large clearance should be provided between engine
unit 12 and footstep 30 to prevent a collision between engine unit
12 and footstep 30. Accordingly, footstep 30 should be provided on
a side more outer in the vehicle width direction in order to
separate footstep 30 from an expanded part 55b expanding outward in
the vehicle width direction (FIGS. 1 and 2) in the case that
expanded part 55b overlaps footstep 30 in the vehicle width
direction, for example.
[0070] In the embodiment, however, the center axis of rotation A1
of secondary sheave shaft 38 is higher than the center axis of
rotation A2 of crank shaft 20 while at least a part of footstep 30
is located behind rear end 29c of generator 29 and under lower end
37d of secondary sheave 37. Accordingly, overlap in the vehicle
width direction between expanded part 55b expanded outward in the
vehicle width direction and footstep 30 is prevented, as shown in
FIG. 4. This allows footstep 30 to be located on a side more inner
in the vehicle width direction. As a result, the vehicle width of
motorcycle 1 can be reduced.
[0071] Footstep 30, as a whole, is preferably arranged to be
provided behind rear end 29c of generator 29 and under lower end
37d of secondary sheave 37. This allows the vehicle width of
motorcycle 1 to be reduced.
[0072] The above effect is enhanced when at least a part of
footstep 30 is located in front of rear end 37e of secondary sheave
37 and behind front end 37f of secondary sheave 37, as described
above. The effect is further enhanced when the whole footstep 30 is
provided in front of rear end 37e of secondary sheave 37 and behind
front end 37f of secondary sheave 37.
[0073] Moreover, as in the embodiment, the center axis of rotation
A1 of secondary sheave shaft 38 may be higher than the center axis
of rotation A2 of crank shaft 20, such that the rear side of engine
unit 12 is higher than its front side, allowing the length of
engine unit 12 in the back-and-forth direction to be reduced. This
allows seat pillar 5 and pivot shaft 5a to be provided on the
further front side, so that rear arm 8 can be made long.
Accordingly, performance of motion of motorcycle 1 is improved.
[0074] Furthermore, pivot shaft 5a is located above at least a part
of footstep 30 and under the center axis of rotation A1 of
secondary sheave shaft 38 in the embodiment. Accordingly, footstep
30 is separated more from the center axis of rotation A1 of
secondary sheave shaft 38. This further reduces interference of
footstep 30 with engine unit 12 in the vehicle width direction.
Accordingly, footstep 30 can be provided on a side more inner in
the vehicle width direction. This results in effective reduction in
vehicle width of motorcycle 1.
[0075] Pivot shaft 5a is preferably provided above an upper end of
footstep 30 and under the center axis of rotation A1 of secondary
sheave shaft 38. This allows the vehicle width of motorcycle 1 to
be especially effectively reduced.
[0076] Further, providing the center axis of rotation A1 of
secondary sheave shaft 38 comparatively upward prevents
interference of an ankle of a foot 60, which is comparatively
projecting, with expanded part 55b. Accordingly, footstep 30 can be
provided in a side more inner in the vehicle width direction, so
that the vehicle width of motorcycle 1 is further effectively
reduced.
[0077] In addition, interference of unit case 50 with pivot shaft
5a is prevented since pivot shaft 5a is provided above at least a
part of footstep 30 and under the center axis of rotation A1 of
secondary sheave shaft 38. This allows pivot shaft 5a to be
provided on the further front side and further improves performance
of motion of motorcycle 1. Pivot shaft 5a is particularly
preferably provided above the upper end of footstep 30 and under
the center axis of rotation A1 of secondary sheave shaft 38.
[0078] In the embodiment, footstep 30 is provided so that upper end
30a thereof is located above lower end 12a of engine unit 12, as
shown in FIG. 4. Accordingly, footstep 30 does not project downward
largely from lower end 12a of engine unit 12. This allows the
vehicle height of motorcycle 1 to be comparatively low.
[0079] In the embodiment, an expanded part (generator case 54 in
the embodiment) is provided in the front half of unit case 50 on a
side deft side) opposite to a side (right side) on which belt type
CVT 14 is provided in the vehicle width direction (FIG. 5). Engine
unit 12 is offset toward the left and footstep 30 is provided
behind the expanded part. Accordingly, the width of motorcycle 1 is
further reduced.
[0080] Providing the expanded part in the front half of unit case
50 on a side (left side) opposite to a side on which belt type CVT
14 is provided in the vehicle width direction causes a space to be
made in a rear half of unit case 50 on the left side. This allows
the width of the rear half of unit case 50 to be narrowed.
[0081] Both the front and rear halves of engine unit 12 on the
right side, however, largely project from center line C2 of engine
13. Accordingly, footstep 30 should be provided so as to be
separated from center line C1 of the vehicle body in the case that
engine unit 12 is provided so that center line C2 of engine 13
would be accorded with center line C1 of the vehicle body as
before. The vehicle width of motorcycle 1 thus cannot be
sufficiently narrowed.
[0082] Narrowing the width of the rear half of unit case 50 on the
left side and offsetting engine unit 12 leftward prevents the left
and right parts of engine unit 12 from expanding. As a result,
footstep 30 provided behind the expanded part can be located more
closely to center line C1 of the vehicle body to prevent the width
of motorcycle 1 from increasing.
[0083] Generator case 54 projecting in the vehicle width direction
is provided in front of footstep 30. Further, a comparatively
expanded part for housing primary sheave 36 of transmission case 55
is located in front of footstep 30. A driver, however, puts his
foot 60 on footstep 30 so that a toe side would widen, as shown in
FIG. 5. Accordingly, it is not a major matter to have an expanded
part in front of footstep 30. Therefore, footstep 30 may be
arranged so that the inner end of footstep 30 is provided on the
inner side of outer end 54a of generator case 54 in the vehicle
width direction. Footstep 30 may be arranged so that the inner end
of footstep 30 is provided on the inner side of outer end 55a of
transmission case 55 in the vehicle width direction.
[0084] That is to say, providing a comparatively large structural
member in a somewhat front side part of unit case 50 and narrowing
the width of a rear side on which footstep 30 is provided in the
back-and-forth direction of unit case 50 as in the embodiment
effectively allows footstep 30 to be provided more closely to
center line C1 of the vehicle body. This results in a narrower
vehicle width of motorcycle 1. Moreover, from this point of view,
cam chain 27 is preferably wound on the left side of crank shaft
20.
[0085] <<Other Modifications>>
[0086] In the embodiment, generator 29 is described as provided on
the left side of crank shaft 20. The invention, however, is not so
limited. An electric motor may be provided instead of generator 29,
for example. That is, a rotation motor functioning both as a
generator and as an electric motor may be provided.
[0087] In the embodiment, footstep 30 is described as a bar-shaped
body extending in the vehicle width direction. Footstep 30,
however, may have other shapes such as the shape of a plate. That
is, footstep 30 may be in any shape having a flat surface part on
which foot 60 is put.
[0088] The invention is useful for a motorcycle, particularly, an
off-road type motorcycle.
[0089] While particular embodiments of the invention have been
described, it should be understood that these embodiments are
exemplary, and not restrictive. Various modifications will be
apparent to those of skill in the art and are within the scope of
the present invention as set forth in the following claims.
* * * * *